Dear Felix, The coordinate system in which the channels are represented is ALS, the native coordinate system of the 4D system.
>From the picture you pasted it seems that the software you use for >visualization makes some assumptions on the orientation of the X/Y/Z axis, >which ssems to be RAS. The sensor positions are represented in the data field ‘grad’. Details about the coordinate system can be found in http://www.fieldtriptoolbox.org/faq/how_are_the_different_head_and_mri_coordinate_systems_defined <http://www.fieldtriptoolbox.org/faq/how_are_the_different_head_and_mri_coordinate_systems_defined> And some instructions for plotting (using Fieldtrip) can be found here: http://www.fieldtriptoolbox.org/tutorial/plotting <http://www.fieldtriptoolbox.org/tutorial/plotting> It is not so clear why you would want to transform the sensors to MNI space for plotting, but the orientation of the axis can be changed by swapping the first and second columns in the chanpos (if that’s what your software needs for visualization). I hope that this helps, Best wishes, Jan-Mathijs > On 14 Dec 2017, at 06:38, Daylin Gongora > <[email protected]> wrote: > > From: Felix Yuan > Sent: Thursday, December 14, 2017 1:20:20 PM > To: [email protected] <mailto:[email protected]> > Cc: Eduardo Gonzalez-Moreira > Subject: HCP resting-state MEG sensor position problem > > Dear HCP experts, > > My name is Felix and I am Prof. Pedro Valdes-Sosa MSc student, during the > last days I had been working with the resting state MEG data from the Human > Connectome Project (preprocessed data). > > Related with this, I am getting an unexpected scalp topography since for > resting state data the alpha activity must be over the occipital areas (see > attached pic occipital_area.jpg). > However, in my analysis the alpha activity appears over the left temporal > lobe for all the subject areas (see attached pic temporal_lobe.jpg). > > Could you please tell me whether the sensor position coordinates that I took > from data.grad.chanpos are right and which space it came from? In which > space are the sensors position and how I could transform it to MNI space? I > have checked on the fieldtrip website and found that there should be a field > , which is data.elec in the data from the preprocessing output of fieldtrip > structure, where can I download it if possible? > > Thanks for your time and help, > All the Best, > > Felix > > _______________________________________________ > HCP-Users mailing list > [email protected] <mailto:[email protected]> > http://lists.humanconnectome.org/mailman/listinfo/hcp-users > <http://lists.humanconnectome.org/mailman/listinfo/hcp-users><occipital_area.jpg><temporal_lobe.jpg> _______________________________________________ HCP-Users mailing list [email protected] http://lists.humanconnectome.org/mailman/listinfo/hcp-users
